Chinanews.com, Beijing, August 26 (Reporter Sun Zifa) In the latest study of the Permian Qianlimestone fossils in Yangquan, Shanxi, the Chinese research team discovered a prehistoric giant shark, which is about 290 million years ago. For the first time, the fossils of the dentate shark were discovered in China.
This major discovery and research in the field of paleontology provides important fossil evidence for the migration of the valvulartooth shark across the Paleo-Tethys Ocean, indicating that the valvulartooth shark already has the ability to migrate across the ocean, and is the top grazing ability in the ancient ocean. Eaters.
This paper was jointly completed by Associate Researcher Gai Zhikun from the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences (Institute of Paleospine, Chinese Academy of Sciences), together with Bai Zhijun from the Bureau of Planning and Natural Resources of Yangquan City, and Zhang Junwen from the Yangquan Branch of the Second Geological Survey of Shanxi Province. Recently, it was published as a cover article by the international professional academic journal "Acta Geologica Sinica (English Edition)".
Associate researcher Gai Zhikun from the Institute of Paleospine of the Chinese Academy of Sciences displayed and introduced the tooth fossils of the tooth shark in the office.
Photo by China News Agency reporter Sun Zifa
A very mysterious group under the true cartilaginous head
The first author and corresponding author of the paper, Gai Zhikun, said in an interview with a reporter from China News Agency in Beijing on the 26th that the flap tooth shark belongs to the cartilaginous fish in the jaws, but it cannot be attributed to the existing cartilage. Either of the two major branches of the fishes, the platyschis and the whole head, it belongs to the more primitive cartilaginous fishes-the true cartilaginous heads.
True cartilaginous heads are called "chimera monsters" by paleontologists. "Chimera" is derived from a fire-spitting monster in ancient Greek mythology. It is usually used to refer to creatures whose bodies are composed of cells from two different lineages.
The weird cartilaginous fishes such as the true cartilaginous heads are called "chimera monsters" mainly because they have both the characteristics of sharks and bony fishes, and many species have mouse-like tails.
Comparison of tooth fossils from Yangquan, Shanxi, 290 million years ago with the teeth of living great white sharks (top).
Photo by China News Agency reporter Sun Zifa
Phalodontidae is a very mysterious group of Euchondral heads. At present, only 17 genera and species have been described, and most of them are scattered tooth fossils.
At present, there are only two complete fossil sharks from the order of the Paratodon, one is the Beranthi shark from Montana, USA, and the other is the Janasa shark from Germany and northern England.
In addition, the tooth shark was the first fossil shark to be discovered and named. It was first named by the name of the dinosaur and the famous British paleontologist Sir Owen.
7 fossil tooth shark teeth found in Yangquan
The fossils of China's petaloid sharks were first discovered in the 1950s by the founder of Chinese paleontology, Mr. Yang Zhongjian, and named "Xingguo petaloid fish" (the era is about 250 million years ago in the Late Permian). However, this fossil specimen of the middle and mandibular teeth of the "Xingguo Pterocephalus" was re-examined in 1978, and was reclassified to another large genus of the Pterocephalus species, the "Pterocephalus".
Associate researcher Gai Zhikun from the Institute of Paleospine of the Chinese Academy of Sciences was interviewed in the office to introduce the latest research results of the fossil shark.
Photo by China News Agency reporter Sun Zifa
Gai Zhikun pointed out that the latest seven fossil tooth sharks found in Yangquan Qian limestone were determined by comparative studies to be the Ohio tooth shark in the genus Pelodon of the genus Pelodon, and it is a true genus of the tooth shark. member.
He said that the fossils of dentate sharks were previously only found in Europe and North America. This time, the first discovery in China has greatly expanded the paleogeographic distribution of dentate sharks in the northern hemisphere, revealing that dentate sharks may be a type of shark that is good at swimming and spreading. Pelagic fishes are also of great significance to the study of the Permian marine biodiversity and the analysis of the paleoenvironment in North China.
This study also shows that the valvulartooth shark has the ability to migrate across the ocean, and further supports that the valvulartooth shark may be a top predator with strong swimming ability, rather than the benthic shellfish originally thought.
Ecological restoration map of the tooth shark in Yangquan, Shanxi 290 million years ago (painted by Yang Dinghua).
Photo courtesy of Institute of Ancient Spine, Chinese Academy of Sciences
The teeth of the valvular shark resemble those of a living great white shark
According to one of the authors of the paper, Lin Xianghong, a research assistant at the Institute of Paleospine, Chinese Academy of Sciences, the extinct flap tooth sharks are a group of primitive species that mainly lived in the Carboniferous to Permian periods (between about 360 million and 250 million years ago). For cartilaginous fishes, the size of the teeth of the dentate shark is similar to that of the living great white shark. It can be inferred that the dentate shark is a prehistoric giant shark with a body length of 3 meters to 5 meters.
Fossil shark tooth shark in Yangquan, Shanxi, 290 million years ago.
Photo by China News Agency reporter Sun Zifa
Petaltooth shark is a worldwide genus and its fossils are widely distributed in major regions of the northern hemisphere such as Europe and North America, but it has not been found in the southern hemisphere so far.
Since most of the bodies of cartilaginous fishes are difficult to preserve, the currently discovered fossils of dentatodon are all scattered teeth. The biggest feature is that there are several rows of horizontal shingled ridge strips under the crown, and the crown part is wide and short.
The scattered state of its fossil preservation also shows that the toothed shark may be like most sharks today, and its teeth are also replaced for life.
Lin Xianghong said that the traditional view is that the squash tooth shark is a bottom-dwelling, slow-moving shell-eating fish that feeds on the bottom-dwelling brachiopods, bivalves and other crustaceans. The edges of the teeth are covered with a large number of vertical grooves and have a huge occlusal surface. This tooth shape may be more suitable for biting the muscle tissue of the prey.
Therefore, the niche of the toothed shark may be similar to that of the modern great white shark, and it was the top predator in the Paleozoic ocean.
Yangquan was a shallow sea near the equator more than 200 million years ago
Shanxi is an important exporter of coal resources in China. Its coal was mainly formed in the Late Carboniferous to Early Permian about 315 million to 270 million years ago.
As early as 1923, the well-known Chinese geologist Li Siguang conducted a geological survey in Shuiquangou in Yangquan area, and discovered 6 layers of limestone here, and named 3 layers of limestone from bottom to top as "Sijieshi" limestone. , "Money Stone" limestone and "Monkey Stone" limestone.
A prehistoric giant shark in the limestone of the Taiyuan Formation in Yangquan, Shanxi Province—the fossil tooth of a tooth shark (photographed by Gai Zhikun and reconstructed by Yang Dinghua).
Photo courtesy of Institute of Ancient Spine, Chinese Academy of Sciences
Bai Zhijun, the discoverer of the fossil shark, said that these three layers of limestone are rich in fossils of echinoderms, brachiopods, cephalopods, and other marine organisms. The underlying rock layers are coal seams, indicating that the Yangquan area was the earliest of the Late Carboniferous. The coal-forming forests in the Permian were affected by transgression events many times, leading to multiple interruptions in coal deposits, resulting in the formation of multiple limestone-sandstone-coal deposits in the Yangquan area. This phenomenon also witnessed the late Paleozoic in the North China Plate. Many times the vicissitudes of life.
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This study focused on the investigation of the dentate sharks and related biota in the Yangquanqian limestone formation, with an age ranging from about 290 million to 298 million years ago.
As a set of biological sedimentary clastic limestone, Qian Limestone is rich in a large number of crinoline stem fossils (hence the Qian Limestone) that resemble ancient coins. In addition, it is accompanied by a large number of brachiopods represented by scallops and stone swallows and other Fossils of marine life represented by cephalopods.
"This shows that more than 200 million years ago, Yangquan was a warm and transparent shallow sea close to the equator, which is very suitable for the survival of all kinds of marine life. In the next step, Yangquan City will rationally develop the geological tourism industry on the basis of protecting fossil resources." Bai Zhijun said.
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